1. Field of the Invention
The present invention relates to a compact wide-angle lens system, and more specifically to a low-cost, compact super-wide-angle lens system for a solid-state image sensor, which super-wide-angle lens system is suitable for a digital image pickup apparatus such as a TV telephone, a video intercom, a monitoring camera, an on-vehicle camera, or the like, which has a favorable optical performance, and which has a total angle of view of approximately 170 degrees.
2. Description of the Prior Art
Wide-angle lens systems for solid-state image sensors have been conventionally widely known. For example, Japanese Patent Application Laid-open No. H6-34879 and Japanese Patent Application Laid-open No. 2001-337268 disclose wide-angle lens system with three-lens-construction. However, these wide-angle lens systems have a total angle of view of 120 degrees which is insufficient to photograph super-wide-angle regions.
On the other hand, Japanese Patent Application Laid-open No. 2004-102162 discloses a super-wide-angle lens system that provides photographed regions with a total angle of view of approximately 170 degrees. However, this super-wide-angle lens system is composed of as very many as eight lens elements in total with a complicated structure and a very long total lens length.